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The short distance behavior of dark matter (DM) at galaxy scales exhibits several features not explained by the typical WIMP DM including velocity dependence of DM cross-sections. We discuss a particle physics model with a hidden sector interacting feebly with the visible sector where a dark fermion self-interacts via a light dark photon as a mediator. We study coupled Boltzmann equations involving two temperatures, one for the visible sector and the other for the hidden sector. It is shown that a hidden sector which starts out very cold eventually thermalizes with the visible sector irrespective of the initial conditions. We fit the velocity dependence of the DM cross-section to the galaxy data consistent with relic density constraint.

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We consider a class of unified models based on the gauge group SO(10) which with appropriate choice of Higgs representations generate in a natural way a pair of light Higgs doublets needed to accomplish electroweak symmetry breaking. In this class of models higher dimensional operators of the form matter-matter-Higgs-Higgs in the superpotential after spontaneous breaking of the GUT symmetry generate contributions to Yukawa couplings which are comparable to the ones from cubic interactions. Specifically we consider an SO(10) model with a sector consisting of 126 + $$ \overline{126} $$ 126 ¯ + 210 of heavy Higgs which breaks the GUT symmetry down to the standard model gauge group and a sector consisting of 2 × 10 + 120 of light Higgs fields. In this model we compute the corrections from the quartic interactions to the Yukawa couplings for the top and the bottom quarks and for the tau lepton. It is then shown that inclusion of these corrections to the GUT scale Yukawas allows for consistency of the top, bottom and tau masses with experiment for low tan β with a value as low as tan β of 5–10. We compute the sparticle spectrum for a set of benchmarks and find that satisfaction of the relic density is achieved via a compressed spectrum and coannihilation and three sets of coannihilations appear: chargino-neutralino, stop-neutralino and stau-neutralino. We investigate the chargino-neutralino coannihilation in detail for the possibility of observation of the light chargino at the high luminosity LHC (HL-LHC) and at the high energy LHC (HE-LHC) which is a possible future 27 TeV hadron collider. It is shown that all benchmark models but one can be discovered at HL-LHC and all would be discoverable at HE-LHC. The ones discoverable at both machines require a much shorter time scale and a lower integrated luminosity at HE-LHC.

An analysis of radiative decays of the neutrinos ν j → ν l γ is discussed in MSSM extensions with a vector like lepton generation. Specifically we compute neutrino decays arising from the exchange of charginos and charged sleptons where the photon is emitted by the charged particle in the loop. It is shown that while the lifetime of the neutrino decay in the Standard Model is ∼ 10 43 yrs for a neutrino mass of 50 meV, the current lower limit from experiment from the analysis of the Cosmic Infrared Background is ∼ 10 12 yrs and thus beyond the reach of experiment in the foreseeable future. However, in the extensions with a vector like lepton generation the lifetime for the decays can be as low as ∼ 10 12 − 10 14 yrs and thus within reach of future improved experiments. The effect of CP phases on the neutrino lifetime is also analyzed. It is shown that while both the magnetic and the electric transition dipole moments contribute to the neutrino lifetime, often the electric dipole moment dominates even for moderate size CP phases.

Higgs boson mass measurement at ∼ 125 GeV points to a high scale for SUSY specifically the scalar masses. If all the scalars are heavy, supersymmetric contribution to the leptonic g − 2 moments will be significantly reduced. On the other hand the Brookhaven experiment indicates a ∼ 3σ deviation from the standard model prediction. Here we analyze the leptonic g − 2 moments in an extended MSSM model with inclusion of a vector like leptonic generation which brings in new sources of CP violation. In this work we consider the contributions to the leptonic g − 2 momentsarising from the exchange of charginos and neutralinos, sleptons and mirror sleptons, and from the exchange of W and Z bosons and of leptons and mirror leptons. We focus specifically on the g − 2 moments for the muon and the electron where sensitive measurements exist. Here it is shown that one can get consistency with the current data on g − 2 under the Higgs boson mass constraint. Dependence of the moments on CP phases from the extended sector are analyzed and it is shown that they are sensitively dependent on the phases from the new sector. It is shown that the corrections to the leptonic moments arising from the extended MSSM sector will be non-vanishing even if the SUSY scale extends into the PeV region. which is about a three sigma deviation from the standard model prediction. Similarly for the electron the experimental determination of g e − 2 is very accurate and the uncertainty is rather small, i.e., one has [4] ∆a e = a This result relies on a QED calculation up to four loops. Thus along with Eq. (1), Eq. (2) also acts as a constraint on the standard model extensions. Supersymmetric theories with low weak scale mass can make corrections to g µ − 2which could be as large as the standard model electroweak corrections and even larger and have strong CP phase dependence [5][6][7] (for early work see [8]). These arise largely from the chargino and sneutrino exchange diagram with the neutralino and smuon exchange diagram making a relatively small contribution. However, if the scalar masses are large, the supersymmetric exchange contributions will be small due to the largeness of the sneutrino and the smuon masses.In this work we give an analysis of the g − 2 for the muon and for the electron in an extended MSSM model with a vector like leptonic generation. We note that vector like multiplets are anomaly free and they appear in a variety of settings which include grand unified models, strings and D brane models [9][10][11][12][13]. Further, it is known that g − 2 has a sharp dependence on CP phases [5][6][7]. For this reason we investigate also the dependence of the muon and the electron g − 2 on the CP phases in the extended MSSM model. Here we are particularly interested in the dependence on the CP phases that arise from the new sector involving vector like leptons. We note that the CP phases are constrained in this case by the electric dipole moment of the electron which currently has the value |d e | < 8.7 × 10 −29ecm [34] while the upper...